When I compared it to my Real Steel, I noticed the plastic housings were different.
When I modified my KWA Vector I cracked the upper housing. The plastic is a brittle ABS like plastic. I called KRISS USA and ordered a replacement upper polymer housing. At first it seemed like a straight forward swap. Far from it. Some of the holes do not line up. So I had to modify the real KRISS polymer housing to get it to fit the KWA Vector components. Next I will swap the lower with a spare lower I have for my real KRISS. Oh and I swapped the real steel stock on too.

Here is a picture of the two upper housings. The top is the KWA and bottom is KRISS USA. (I wish I could have gotten the real SMG upper).

You can see how the plastic of the KWA has a texture to it and the real KRISS doesnt.

You can sort of see how the top three holes dont match between housings.

Taking the fire control group was rather easy. Here is a side by side comparison with my out of spec KRISS SMG FCG housing and the KWA SMG FCG. They are very similar.

I like to use a Surefire SR07 tape switch cause it has a constant clicky and momentary the all in one. The problem is that the tape switch clamps onto rails and is too big to fit in the narrow slot. I drilled a hole thru the side so the plug part can fit thru and plugin to the light. My drill bit grabbed a part of the housing and torqued it rather than cut it. So it cracked the housing.

Update. I got my spare housing swapped out and put it on the KWA KRISS.

So now my KWA Vector SMG exterior components is all real steel. Only the internals are airsoft.

The lower housing swap was much easier. The only issue is the anchor hook for the charging handle return spring. It did not want to come out of the KWA housing. So I will need to order a replacement from KRISS USA.

I followed the Armorer's Course. There are some aspects not mentioned in there. You need to remove the mag catch, the last round bolt catch, and the charging handle return spring anchor.

KWA Housing on top and Real KRISS housing on bottom.

Naked KRISS Carbine lower.

KWA KRISS with lower installed. Now the only KWA Airsoft parts are the internals. All exterior parts are from Real KRISS Vector.

Oh and here is what my KRISS Carbine looks like. I had my spare housing cerakoted.